The concentration of the enzymes creatine kinase (CK) and aspartate aminotransferase (AST), that are released from damaged muscle, was measured in the blood of wild adult male mallards (Anas platyrhynchos) captured for banding in decoy and bait traps and by rocket net. The concentration of CK and to a lesser extent AST was elevated markedly in ducks captured by all methods, indicating muscle injury. The level of CK was significantly greater in ducks captured in decoy traps and rocket net than in those captured in bait traps. This elevation appeared to be related to the length of time the birds were restrained and to the method of restraint.